Crime Writer Seeking Forensic Information

by Larry
(UK)

I am writing a crime fiction novel and need some accurate forensic information. And would like to thank you in advance for your time.

At the beginning of the story, a young woman is raped and held down by another. Her partner comes home and is attacked (knocked unconscious). One of the attackers then slit's her throat. Her partner is charged with her rape and murder. When police officers first arrived at the crime scene, the boyfriend was cradling the victim in his arms. They were both naked and soaked in the victims blood. The knife used to slit her throat was laying by his side covered in his prints. The victim had traces of her boyfriends skin under her fingernails.

The forensic guys had told the investigating officers that she was probably trying to fight the boyfriend off, scratching his neck as she fought for her life. The PM showed that the victim's body and genitalia had been scrubbed clean - a bowl of bloodied water, brushes and towels lay close by. The investigating officers belief that the boyfriend was in the middle of cleaning up after himself, when feelings of remorse over what he had done took over. The only DNA found on the victim was that of the boyfriends.

Forensic Question: If a woman is raped and the guy wore a condom then washed the genitalia and body afterwards would there be sufficient/any DNA/bodily fluids?

Help: If I've got it wrong, how could the real killers have staged it so that the boyfriend takes the wrap?

I want to make sure the content is as close to factual as a book of fiction needs to be.

Regards

Larry